Cable shield clamp

ABSTRACT

Two identically curved strips are intermeshed and bolted together to provide a circular clamp for making electrical connection with the ribbon shield of a power cable.

[ 1 Oct. 29, 1974 CABLE SHIELD CLAMP 2/1927 Feige 339/251 FOREIGNPATENTS OR APPLICATIONS Inventor: Ronald D. Taylor, Blaine, Minn.

[73] Assignee: Minnesota Mining and Manufacturing Cmnpany, St Paul,873,932 4 1942 339 251 France.,.............

5/1956 Germany.............

22 Filed: Aug. 2, 1973 21 Appl. No.: 384,932

Primary Examiner-loseph H. McGlynn Attorney, Agent, or FirmAlexander,Sell, Steldt & DeLaHunt [57] ABSTRACT Two identically curved strips areintermeshed and 52 us. 339/14 L, 24/115 A, 24/135 K, 24/284, 174/40 cc,339/251 [58] Field of Search............ 339/14, 251

bolted together to provide a circular clamp for making 24/135 2791 284;174/40 CC electrical connection with the ribbon shield ofa power cable.

7 Claims, 5 Drawing Figures References Cited UNITED STATES PATENTS813,526 Simpson......................,...... 339/251 CABLE SHIELD CLAMPThis invention relates to electric power distribution and is concernedparticularly with improvements in the grounding of tape or ribbonshielded high voltage power cable.

In making a running splice in power cable it is necessary to join notonly the ends of the current-carrying conductors but also the ends ofthe ribbon shields. For the latter purpose, conventional practice hasinvolved installing jumper wires or cables across the splice. Prior artclamping devices of adequate strength and currentcarrying capacity haveinvariably been bulky, difficult to install, or otherwiseunsatisfactory. Soldering of the jumpers to the shields results in amore compact structure but is difficult to accomplish under fieldconditrons.

The clamp of the present invention is simple in construction, easilyapplied, and of fully adequate mechanical strength and electricalcurrent-carrying capacity.

In the drawing,

FIG. 1 is an elevational view showing two of the clamps of FIGS. 2 and 3in use at a power cable splice area, the cable and cover being shown inphantom;

FIG. 2 is a plan view of a blank;

FIG. 3 is a sectional elevation of an assembled clamp as shown in FIG.1, taken approximately at line 3 3 thereof;

FIG. 4 is a sectional elevation showing a modified form of clamp withpre-connected jumper cable; and

FIG. 5 is a plan view of a blank for an alternative form of clampmember.

Each clamp consists of two identically curved generally L-shaped platesl1, 12 held together in opposing and intermeshing relationship by a bolt13 and nut 14. Each plate is centrally perforate within a flat or veryslightly laterally warped end portion 15; the remainder of the plate iscurved along a circular path and extends over approximately 240 degreesof arc. The end 15 extends radially from the curved portion. The curvedcentral segment 16 retains the full width of the end 15; the curvedextension 17 is slightly less than one-half of such width. When placedtightly face-to-face as in FIGS. I and 3, the two pieces intermesh tocomplete the circle at full width, and the curved portions areterminally unconnected.

In a specific Example for use with 15 KV ribbonshielded power cable, theclamp members are made from a resilient plate of beryllium copper alloyNo. 172 (Berylco 25"), A hard, 0.025 inch thick. The blanks are each3.219 inches long and 1.25 inches wide. The end 15 is 0.700 inch long;the narrow extension 17 is 1.252 inches long and 0.600 inch in width.The segments l6 and 17 are curved to an inside diameter of 1.200 inches.The pieces are hardened by heat treatment to a Rockwell hardness, Cscale, of 38-42, and are lightly tin plated.

The method of application will be readily apparent on consideration ofFIG. 1. The two halves are slipped over the bared shielded cable-endsinto face-to-face intermeshing contact, the resiliency of the piecesbeing fully adequate for the purpose. Ajumper wire 19 of sufficientload-carrying capacity, previously provided with perforate contactterminal lugs 20, is fitted onto bolts 13 which are passed through thealigned perforations in the two pieces, and nut 14 is tightened in placeto hold the assembly firmly together.

The stiffness and resiliency of the hardened alloy are such that, onceapplied, the clamp cannot be moved by hand. Full electrical contact isobtained, and the current-carrying capacity is entirely adequate for theintended use.

FIG. 4 illustrates a modified clamp 40 wherein one.

clamp member 42 is raised within the full width central portion 46 toprovide a rounded loop 48. A segment 45 of a jumper, in this case astranded cable, is preattached within the loop by soldering as shown at47. The two halves 41, 42 are held together by bolt 43 and nut 44. Thefree end of the jumper cable 45 is to be connected to the free end ofthe corresponding cable of an opposing clamp assembly in a splicesituation as described in connection with FIG. 1, e.g., by bolt or othercable-joining means, not shown; alternatively, the free end may beconnected directly to ground, e.g., in a termination situation.Advantages of this structure are that the cable-ends may be attached tothe clamps prior to installation, may be of any length and easilyadjustable to any length of splice area, and are easily interconnectedat any desired point. The loop 48 adds to the spring compression reserveof the assembled clamp and this modification is particularly useful oncables of larger diameter and current-carrying capacity.

Another modification is shown in FIG. 5, wherein the terminal extensionof the central segment 56 of the generally L-shaped blank 51 isbifurcate, the two legs 57 and 58 intermeshing with similar extensionsof an opposing blank when the two are formed and combined as describedin connection with FIGS. 1 and 3.

What is claimed is as follows:

1. A clamp comprising a pair of rigidly resilient generally L-shapedelectrically conductive metal plates each formed to provide asubstantially flat centrally perforate end section, a curved centralsection of the same width as said end section, and a curved extension ofslightly less than one-half of said Width, the curved portions togetherextending over significantly more than one-half but less thanthree-fourths of a complete circle, the perforate end section beingradially extended from said circle, the two pieces fitting together inface-to-face relationship with the curved portions terminallyunconnected to define a circular clamping area.

2. Clamp of claim 1 wherein said central section and said extension eachextend over approximately of arc.

3. Clamp of claim I wherein said curved extension is in two parallelparts bifurcate.

4. Clamp of claim 1 including fastening means applied through saidperforate end sections for holding said pair of plates together inface-to-face interfitting relationship.

5. Clamp of claim 4 including electrically conductive jumper meansattached thereto.

6. Clamp of claim 4 wherein one of said pair of plates includes a raisedloop within the central section for solder connection with a jumpercable.

7. Clamp of claim 6 including a jumper cable segment soldered into saidloop.

1. A clamp comprising a pair of rigidly resilient generally Lshapedelectrically conductive metal plates each formed to provide asubstantially flat centrally perforate end section, a curved centralsection of the same width as said end section, and a curved extension ofslightly less than one-half of said width, the curved portions togetherextending over significantly more than one-half but less thanthree-fourths of a complete circle, the perforate end section beingradially extended from said circle, the two pieces fitting together inface-to-face relationship with the curved portions terminallyunconnected to define a circular clamping area.
 2. Clamp of claim 1wherein said central section and said extension each extend overapproximately 120* of arc.
 3. Clamp of claim 1 wherein said curvedextension is in two parallel parts bifurcate.
 4. Clamp of claim 1including fastening means applied through said perforate end sectionsfor holding said pair of plates together in face-to-face interfittingrelationship.
 5. Clamp of claim 4 including electrically conductivejumper means attached thereto.
 6. Clamp of claim 4 wherein one of saidpair of plates includes a raised loop within the central section forsolder connection with a jumper cable.
 7. Clamp of claim 6 including ajumper cable segment soldered into said loop.